Fragmentation genetics of Vateriaindica: implications for management of forest genetic resources of an endemic Dipterocarp

Tropical agro-forest landscapes are potentially valuable reserves of forest genetic resources for forestry and restoration of degraded forests. The Dipterocarpaceae is a dominant Southeast Asian family of tree species of global significance for the tropical timber industry. Very little information exists about how effective human modified landscapes are for conserving genetic diversity in dipterocarp species. This study provides a baseline for understanding how fragmented agro-forest landscapes in India sustain forest genetic resources in an endemic dipterocarp tree. We compare genetic diversity and fine-scale spatial genetic structure (FSGS) in the threatened tree species Vateria indica within an isolated and a continuous forest site in the Western Ghats, South India. We place these results in the context of dipterocarps from both the Seychelles and Borneo. Parentage analysis of 694 progeny using twelve nuclear microsatellite markers is applied to estimate pollen and seed dispersal. Using a nursery trial we evaluate effects of inbreeding on growth performance. Our results show that levels of FSGS, and gene dispersal are comparable between a small isolated and a large continuous site of V. indica. Realized long-distance pollen flow into the isolated patch appears to help maintaining genetic diversity. The nursery experiment suggests that selection favours outbred progeny. Individuals of V. indica in close proximity appear less related to each other than in another highly fragmented and endangered dipterocarp species from the Seychelles, but more related than in three dipterocarp species studied in continuous forest in Borneo. We discuss the wider implications of our findings in the context of conservation and restoration of dipterocarp forest genetic resources in fragmented populations.